Various sign boards or frames have been utilized heretofore for mounting removable letters and numerals therein. Such letters and numerals have been retained in such frames by various retaining means such as adhesives, or fitting in slots, for example. Many of such sign boards or frames are designed for outdoor use and have been formed of various types of rigid materials, such as wood, metal or rigid plastic material. Oftentimes, a backing is required for supporting the removable letters. Puzzles utilizing the placement of interfitting pieces have normally comprised the placement of preselected pieces on the back of a puzzle frame which provides support for the pieces.